1. Field of the Invention
The present invention relates to a weighing scale capable of detecting bottoming that hinders the accurate measurement of a weight, and also to a method of controlling a weighing scale.
2. Description of Related Art
There is a type of error state that can occur when using a scale for weighing, which is called “bottoming” (i.e., “reaching the bottom” or “bottoming out”). The bottoming refers to a phenomenon in which the bottom portion of a base plate unit of a weighing scale touches a floor surface when a load is applied. This phenomenon sometimes takes place, for example, when taking the weight of a human by using a body weighing machine, which is a type of weighing scale, when the body weighing machine is placed on a flexible floor surface such as a carpet or a tatami mat (Japanese straw mat flooring) or on an unlevel floor surface. When this bottoming takes place, the bottom portion of a base plate unit receives a reaction force from the floor, and as a result, a measured weight will be less than the actual weight, which is an error state.
As a technique for coping with this bottoming, there is disclosed, for example, in Japanese Patent Application Laid-Open Publication No. 8-247832, a plane soleplate provided on the bottom portion of the base plate unit in a removable manner. As another conventional technique, which is commonly used, extension members for extending the leg portions supporting a base plate unit are provided in a removable manner, so as to create sufficient distance between the base plate unit and the floor surface.
In the conventional technique, the bottoming can be avoided by mounting the soleplate or the extension member if a user is aware of the problem. However, a typical user may not always be able to appropriately decide whether the floor surface on which a body weighing machine is placed is suitable for measurement. A user might not even be aware of an error even if the measurement error is caused by the bottoming because the user might misunderstand the erroneous measurement result indicating less weight and think that it indicates actual loss of weight.